PHYLUM ANNULATA 



507 



leads by a narrow ciliated duct into a receptacle, in which leuco- 

 cytes laden with waste-matters are received from the coelomic 

 spaces and sinuses, subsequently 

 to undergo degeneration and 

 absorption (Fig. 422). By its 

 outer side this receptacle is in 

 close relation to the inner end 

 of the nephridium, and the 

 waste-matters from the disin- 

 tegrated leucocytes are no doubt 

 received into the nephridial 

 canals and thus passed out to 

 the exterior. In Hirudo and 

 Herpobdella (Nephelis) the re- 

 ceptacles appear to be the 

 organs in which new blood- 

 corpuscles are manufactured. 

 The ciliated funnels of the Hiru- 

 dinea correspond more closely 

 with the ccelomoducts or ciliated 

 organs of the Polychaeta than 

 with the nephrostomes ; they 

 are to be compared also with the 

 " urns " of the Sipunculoidea. 

 In the Rhynchobdellid Ponto- 

 bdella a very interesting modifi- 

 cation of the nephridial system 

 occurs. Instead of distinct neph- 

 ridia, there is found on the 

 ventral surface of the body a 

 very complex network (Fig. 423, 

 nph.), which sends off on each side of each segment a short branch 



terminating in a ciliated funnel, and 

 a similar branch which opens ex- 

 ternally (np.). A similar modifica- 

 tion occurs in Branchellion. 



The nervous system always 

 closely resembles that of Hirudo, as 

 also do the sense-organs. The 

 number of eyes is subject to con- 

 siderable variation : they may be 

 developed on the posterior sucker, or 

 may be absent altogether. 



Reproductive Organs. The 



^i^^^^^fr^^ testes U8U * U y have the . segmental 

 of nerve-cord ; np'. nephridiopore ; arrangement found in Hirudo, their 

 fiftffiraSfi&tf c '"' number varying from five to twelve 



fel o( Herpobdella 



(Clepsine). cr. crown-cells of funnel ; ex. 

 terminal cell of the nephridium; Ic. leuco- 

 cy tes ; st. duct leading to receptacle \w. wall 



f (From Mei8enheimer > after 



